For the transportation and storage of irradiated nuclear reactor fuel elements, it is customary to utilize shielded transport and storage containers made of spheroidal cast iron or steel. The inner chamber of the containers can have a round or square cross-section. Containers with a circular inner chamber have the advantage of being easier to manufacture and of optimally utilizing the storage space. The irradiated fuel elements are received in these storage containers in special insert cages.
In addition to the accommodation of complete fuel elements, it has already been proposed to disassemble the fuel elements and to load the individual fuel rods of these fuel elements closely packed into a storage container. Considerable space savings can be achieved thereby. European Pat. No. 0005623 discloses that the storage container is thus capable of holding a larger amount of fuel elements.
According to a state-of-the-art disclosure made in German published patent application No. DE-OS 3,222,822, the fuel rods removed from the fuel elements are closely packed into cans the geometry of which corresponds approximately to one fuel element. The filled cans are then placed into the receiving shaft-like compartments of the insert cage, these compartments being actually configured to hold the fuel elements.
An important technical problem of the storage of individual fuel rods packed as closely as possible in a storage container is the temperaure control of this storage unit. As a result of the decay heat of the radioactive fuel, the temperature within the storage unit may increase inadmissibly. Dissipating the heat from the interior of the fuel rod package involves problems. Consequently, this heat dissipation problem may be the reason for limited packing densities or extended previous decay times of the fuel elements until they can be loaded into the storage container.